Photo-electric device



1,568,694 w. A. RUGGLES PHOTO ELECTRIC DEVICE Jan. 5 1926. 7

Filed April 16, 1921 Inventor \Xfllliam A. Fluggles,

His Attorney.

electrode which common y Patented Jan. 5, 1926.

UNITED "STATES 1,568,694 P'ATENT o FicE;

WILLIAM A. RUGGLES, OF SCHENECTADY, NEW YORK, ABSIGNOR 'IO GENERAL ELEC-TRIO COMPANY, A CORPORATION OF NEW YORK.

PHOTO-ELECTRIC DEVICE.

Application filed April 16, 1921. Serial No. 462,052.

To all whom it may concern:

Be it known that I, WILLIAM A. RUGGLES', a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Photo-Electric Devices,of which the following is a specification.

The present invention relates to the preparation of photo-electricdevices and includes in particular a new method of forming theconductive sup ort for an active is constituted by a film oflight-sensitive metal, as, for example, potassium. v

Heretofore, a conductive backing for the active electrode material hasbeen prepared by depositing a film of silver from an aqueous solutionupon the inner surface of a glass bulb. Upon ordinary drying, potassiumwas admitted to the bulb in the presence of air and deposited upon thebacking metal. The resulting electrode inevitably contained variousimpurities, notably oxidation products and occluded moisture, which werea source of variability in the photo-electric device.

In accordance with my invention, I have provided a photo-electricelectrode of imby depositing a film of proved sensitivity to serve as aconductive metal in a vacuum base for the light-sensitive metal whichpreferably is deposited likewise in a vacuum upon the conductivefoundation surface. My invention includes also new methods of preparingmetal films as set forth with greater particularity in the appendedclaims.

In the accompanying drawing, Fig. 1 illustrates in perspective a deviceto which my invention is applicable, the bulb wall being in part brokenaway, and Fig. 2 is an enlarged view of a slightly modified heaterelectrode with a bead of volatilizable metal attached.

The device shown in the drawing comprises a glass bulb 1 having a sidearm 2 containing a glass stem 3 into which are sealed electricconductors 4, 5. Attached to these conductors is a vaporizer which isconstituted by a coiled filament 6 consisting of a refractory metal, as,for example, tungsten,-molybdenum or tantalum. The conductor 5 also actsas a support for a coneshaped body 7 consisting of nickel, or othersuitable material, which acts as a shield to prevent deposition of metalupon part of the bulb. It is not necessary that the shield 7 should havethe particular shape illustrated. A cone or pyramidal shape isprefarable, as it reduces loss of light when the device 18 111 use,'raysof light striking the shield being reflected to the side walls upon thesensitive electrode. A shield 8 intercepts metal articles projected fromthe filament 6, as escribed below to prevent silvering of the innersurface of the side arm 2 which might cause electrical shert-circuiting.

The bulb 1 is first carefully freed from moisture by baking at atemperature close to but below the softening temperature of glass, say,at 360 C. The bulb is then exhausted through the tubulation 9, acondensation pump preferably being used.

A bead of easily volatilizable metal, as, for example, silver, gold, orcopper, is affixed to the filament 6 before sealing in the stem 3, asshown at 10 inFig. 2. The filament 6 is heated by passage of current tothe volatilizing templerature of the bead 10 when the bulb as been wellexhausted, say, to a vacuum of about 5 micron (0/0005 mm. of mercury),the molten bead clingin to the turns of the coiled filament while t emetal is volatilizin'g. The metal vapor is projected radially in theevacuated bulb interior and is condensed upon the inner surface of thebulb which is artificially cooled if necessary; for exam le, byimmersing the bulb in water. The eposited metal film makes electricalcontact with a sealed-in electrode 11 consisting of platinum or othersuitable material. The shield 7 will shadow a portion of thebulb, asindicated at 12, which is left clear-of deposit as the metal vapor mehigh vacuum travels in straight lines. Thereupon the bulb is againheated and with the vacuum unbroken and the vacuum pump in constantoperation, a light-sensitive material, for example, metallic potassiumis introduced as a vapor into the bulb. Conveniently, the potassium, orother suitable light-sensitive material, may be contained in a smallbulb 13 intercalated in the vacuum line 9, heat being applied in anyconvenient way to volatilize the same. In order to render the potassiumfree from im urities, I prefer to introduce the same in t e unavoidablyoxidized state into a side chamber 14, as indicated at 15. After thesilver or other metal has been deposited as above described, the chamber14 is heated to distill the potas sium into an adjoining chamber 16where it distills as indicated by the dotted lines, the bulb 13 and thedevice 1 being gently heated. Thereupon the potassium is distilled inturn into the bulb 13 and then into the device 1. The potassiumcondensed upon the window 12 can be driven off by external heating.

The photo-electric device now may be subjected to a sensitizingtreatment by admitting hydrogen at a pressure ofsay, 100 microns ofmercury, and passing a suitable current through the device, the hydrogeneventually being replaced by argon gas but these steps in themanufacture of the photo-electric device subsequent to the formation ofthe film electrode forms no part of my present invention. The completeddevice is finally sealed off by fusion at 17 in the usual manner.

During the operation of the device, light rays are admitted through thewindow 12 and impinge either directly or by reflection from the surfaceof the shield upon the surface of the film electrode which acts as acathode, causin an electron current to be emitted. The filament 6 andthe shield 7 functions as anode in the completed device, the filamentbeing'unheated. The photoelectric device produced as herein described ismore sensitive and reproducible in its characteristic than devicesformerly made by chemical methods.

\Vhat I claim as new and desire to secure by Letters Patent of theUnited States, is,-

1. The method of preparing a light sensitive device which consists indepositing metal upon the inner surface of an evacu ated container, anddepositing a hoto-sensitive material upon said sur ace while maintainingsaid vacuum.

2. A photo-electric device comprising a sealed bulb, a film ofconductive material upon the inner surface of said bulb, said film beingformed by the deposition of metal vapor in a vacuum, and having a cleararea constituting a window formed by shielding a portion of said bulbsurface from said vapor, a light-sensitive material superimposed uponsaid film and a cooperating electrode.

3. The method of preparing a cathode in a photo-electric device havingan insulating container which consists in evacuating the container at anelevated temperature, depositing by vaporization a metal film upon theinner surface of said container except for a region through which lightis to be admitted while keeping said vacuum unbroken, and depositing aphotoelectric material upon said film.

4. The method of preparing a photo-electrio device comprising a glasscontainer, which consists in removing gas from the walls and the spacewithin said container, depositing a metallic film on the inner surfaceof said container and thereupon depositing a light-sensitive material,the vacuum remaining unbroken during the latter two operations.

The method of depositing a conductive film upon a non-conductive supportadapted to receive the active material in a photoelectric device whichcomprises evacuating said device, vaporizing a metal in the evacuatedspace in said device, maintaining said foundation cool enough tocondense vapor thereon and mechanically shielding portions of thesupport which is to be maintained clear from deposit.

6. The steps in the preparation of a photo-electric device whichconsists in evacuating said device at an elevated temperature,vaporizing a metal in said device while maintaining said vacuum intact,cooling the portion of the envelope of said device to deposit a film ofmetal thereon, shielding another portion of said envelope from a depositof said metal and thereupon depositing a light sensitive material uponsaid film while keeping said vacuum unbroken.

7. The method of preparing a photo-sensitive electrode which consists incoating a gas-free interior surface of an evacuated envelope with alayer of metal in the absence of water, and thereupon depositing a layerof photo-sensitive material on said coating.

8. A photo-electric device comprising a bulb, a shield within said bulb,the inner surface of said bulb being coated with metal layer formed bycondensation from vapor in a vacuum and having a clear space whereoncondensation has been prevented by said shield which constitutes areflector in said device.

9. A photo-electric device comprising a bulb containing an attenuatedgas, a conductive metallic film upon the inner surface of said bulbexcept for a clear area constituting a Window, a leading-in conductortherefor, a photo-sensitive material upon said film, a cooperatingelectrode and a light reflector in said bulb opposite said window.

Inwitness whereof, I have hereunto set my hand this 15th day of April,1920.

. WILLIAM A. RUGGLES.

